Internet
The Internet Protocol (IP) as we know it today was designed during the late 70's when a 32 bit (2.sup.32 or as represented in 4-8 bit messages, e.g. 255.255.255.255 later called Ipv4) message permitted approximately 4.25 billion unique addresses. It was thought at that time this would be more than enough address space to satisfy future needs. IP was still experimental and was focused on by academia and for academia. Personal computers were still a prediction.
By the 90's it was clear that Ipv4 addressing was going to be exhausted, some thought as early as 1995. The result was the commissioning of Ipv6, through the development of a task force called Internet Engineering Task Force (IETF). A key charter for this task force was interoperability, forward and backward.
The basic structure of the new addressing scheme is a 128 bit message represented as 8-16 bit messages separated by a colon, and represented in a hex format, (e.g. FFFF:FFFF: . . . in hex, 65535:65535: . . . in dec. and 1111111111111111:1111111111111111: inbinary). The combination of available addresses is approximately 3.4.times.10.sup.38 unique addresses, enough to certainly take care of network addressing for the next millennium if not the non-foreseeable future.
As part of the IETF scheme, a binary prefix has been set aside (100), which represents 1/8 of the available network addressing. This was set aside and made available for geographic-based addressing. Unicast is defined as a resolved or assigned address or a unique identifier for a single interface, i.e. a packet sent to a unicast address is delivered to the interface identified by that address.
TCP/IP represent connection/connectionless protocols in the Open Systems Interconnect (OSI) reference model. OSI is a standard reference model for communication between two end users in a network. It is used in developing products and understanding networks. The OSI Reference Model describes seven layers of related functions that are needed at each end when data is sent from one party to another party in a network. An existing network product or program can be described in part by where it fits into this layered structure. For example, TCP/IP is usually packaged with other Internet programs as a suite of products that support communication over the Internet. This suite includes the File Transfer Protocol (FTP), Telnet, the Hypertext Transfer Protocol (HTTP), e-mail protocols, and sometimes others.
The OSI model describes the flow of data in a network, any IP network, from the lowest layer (the physical connections i.e. cell phones) up to the layer containing the user's applications. Data going to and from the network is passed layer to layer. Each layer is able to communicate with the layer immediately above it and the layer immediately below it.
The OSI Reference Model includes seven layers:
1. The Application layer represents the level at which applications access network services. This layer represents the services that directly support applications. PA0 2. The Presentation layer translates data from the Application layer into an intermediary format. This layer also manages security issues by providing services such as data encryption, and compresses data so that fewer bits need to be transferred on the network. PA0 3. The Session layer allows two applications on different systems to establish, use, and end a session. This layer establishes dialog control between the two computers in a session, regulating which side transmits, plus when and how long it transmits. PA0 4. The Transport layer handles error recognition and recovery. It also repackages long messages when necessary into small packets for transmission and, at the receiving end, rebuilds packets into the original message. The receiving Transport layer also sends receipt acknowledgments. PA0 5. The Network layer addresses messages and translates logical addresses and names into physical addresses. It also determines the route from the source to the destination computer and manages traffic problems, such as switching, routing, and controlling the audio signals or data. PA0 6. The Data Link layer packages raw bits from the Physical layer into frames (logical, structured packets for data). This layer is responsible for transferring frames from one computer to another, without errors. After sending a frame, it waits for an acknowledgment from the receiving computer. PA0 7. The Physical layer transmits data from one system to another and regulates the transmission of data over a physical medium. This layer defines how the cable is attached to the device and what transmission technique is used to send data over the system.
When two devices communicate on a network, the software at each layer on one system assumes it is communicating with the same layer on the other system. For example, the Transport layer of one system communicates with the Transport layer on the other system. The Transport layer on the first system has no regard for how the communication actually passes through the lower layers of the first system, across the physical media, and then up through the lower layers of the second system.
Although TCP fits well into the Transport layer of OSI and IP into the Network layer, the other programs fit rather loosely (but not neatly within a layer) into the Session, Presentation, and Application layers. In this model, we include only Internet-related programs in the Network and higher layers. OSI can also be applied to other network environments to include voice. A set of communication products that conformed fully to the OSI reference model would fit neatly into each layer.
With the advent of Ipv6 or Ipng, the number of network interfaces can be expanded beyond the network to individual devices. A real time and secure unicast point essentially can be extended to the individual user through a concept called anycast, defined as a communication between a single sender and the nearest of several receivers in a group. The term exists in contradistinction to multicast, communication between a single sender and multiple receivers, and unicast, communication between a single sender and a single receiver in a network. Anycasting is designed to let one host initiate the efficient updating of routing tables for a group of hosts. IPv6 can determine which gateway host is closest and sends the packets to that host as though it were a unicast communication. In turn, that host can anycast to another host in the group until all routing tables are updated.
The anycast allows the unicast interface to now function as a unicast link to the device, its address is unique and its interface is virtual to the Internet backbone. By extending this concept to devices other than classical interface devices, e.g. a computer and network, and by further expanding the addressing scheme, we have created the ability to transfer data, for all intents and purposes, nearly real time and secure. Ipv6, unicast links and anycast are key elements to tunneling protocols, protocols needed to reduce network latency for data transfer.
Relative to the Internet, tunneling is using the Internet as part of a private secure network. The "tunnel" is the particular path that a given message or file might travel through the Internet. A protocol or set of communication rules called Point-to-Point Tunneling Protocol (PPTP) has been proposed that would make it possible to create a virtual private network through "tunnels" over the Internet. This would mean that devices would no longer need Independent Service Provider (ISP) support for wide-area communication but could securely use the public networks in near real time. PPTP, sponsored by Microsoft and other companies, and Layer 2 Forwarding, proposed by Cisco Systems, are among the main proposals for a new Internet Engineering Task Force (IETF) standard. With PPTP, which is an extension of the Internet's Point-to-Point Protocol (PPP), any user of a communications device with PPP client support will be able to use an ISP to connect securely to a device elsewhere in the domain.
PPP is a protocol for communication between two devices and is a full-duplex By protocol that can be used on various physical media, including twisted pair or fiber optic lines or satellite transmission. It uses a variation of High Speed Data Link Control (HDLC) for packet encapsulation. PPP is usually preferred over the earlier de facto standard Serial Line Internet Protocol (SLIP) because it can handle synchronous as well as asynchronous communication. PPP can share a line with other users and it has error detection that SLIP lacks. Where a choice is possible, PPP is preferred.
A virtual private network (VPN) is a private data network that makes use of the public telecommunication infrastructure, maintaining privacy through the use of a tunneling protocol and security procedures. A virtual private network can be contrasted with a system of owned or leased lines that can only be used by one company. The idea of the VPN is to give the user the same capabilities at much lower cost by sharing the public infrastructure. Phone companies have provided secure shared resources for voice messages.
A virtual private network makes it possible to have the same secure sharing of public resources for data. Users today are looking at using a virtual private network for both extranets and wide-area Intranets. Using a virtual private network involves encrypting data before sending it through the public network and decrypting it at the receiving end. An additional level of security involves encrypting not only the data but also the originating and receiving network addresses. Although as yet there is no standard protocol, Microsoft, 3Com, and several other companies have proposed a standard protocol, the Point-to-Point Tunneling Protocol (PPTP) and Microsoft has built the protocol into its Windows NT server.
GPS
The Global Positioning System or "GPS" was born as a result of the problems experienced by the US military forces during the Vietnam conflict. One of the main difficulties for the troops on the ground was how to keep in contact with each other, especially due to the harsh jungle terrain. A localized LORAN system was in use, but this was subject to the errors common to all radio systems, such as ground wave deflection and poor radio reception at night and in bad weather. The US then experimented with a system of 4 satellites, initially named TRANSIT. These were in high orbit above the earth and available to marine users as well as the military. However, the system was largely inaccurate, as position fixes could only be obtained every 2 hours at best.
The NavStar system was developed next and was operational in a limited way from 1986, but there was only 3-4 hours coverage per day due to the small number of satellites in orbit. The GPS system became "partially operational" when hostilities began in the Gulf in 1990. Here, experimental Block 1 satellites were used in addition to the established Block 2 satellites, thus giving a useable constellation of 21 satellites. The Department of Defense made the system operational for civilian users in 1990, which is the same GPS system we use today.
The GPS satellites orbit the earth twice a day, 11,000 miles above the earth, transmitting their precise position and elevation. The GPS receiver acquires the signal, then measures the interval between transmission and receipt of the signal to determine the distance between the receiver and the satellite. Once the receiver has calculated this data for at least 3 satellites, its location on the earth's surface can be determined.
Every satellite transmits almanac and ephemeris data. Almanac data is general information on the location and the health of each satellite in the constellation, which can be received from any satellite. A receiver with a current almanac in its memory knows where in the sky to look for satellites, given its last known position and the time of day. Ephemeris data is the precise satellite positioning information that is used by the GPS receiver to compute its position. Each satellite transmits its own ephemeris data.
There are also 2 distinct signal types emitted from the satellites; CA (Coarse Acquisition) and PPS (Precise Positioning System). CA coded signals can give 15 meter RMS (Root Mean Square) accuracy. However, the DOD has introduced a random error into the system, known as Selective Availability. This means that the satellites will randomly give out an error signal, thus degrading the accuracy of the signals to 100 meters officially, although accuracy is usually 50 meters. PPS is only available to licensed, mainly military, users and can give sub-1 meter accuracy.
With the advent of this technology, its subsequent commercialization, its evolution in size, cost and accuracy, GPS is rising to the surface as a technology available to systems not classically considered either compatible, available or necessary until the recent past.
Wireless Communications
Cellular (wireless) communications has evolved from analog to digital over the past few years. These streams of data are sent utilizing protocols standardized in the telecommunications industry. They are referred to as GSM, CDMA, TDMA etc., each one unique but developed as a voice under data concept. Some have evolved to purely digital but in the overall telecommunications network it is still voice on voice networks. These highspeed digital communications have the ability to be supported by TCP/IP in a purely digital environment.
Heretofore these three distinct fields of technology--Internet data communications, global positioning system and wireless communications have evolved largely independently; each addressing its own challenges and commercial markets. The present application results from rethinking these technologies in a broader context, and exploring ways in which they overlap, or could overlap, to provide new functionality and efficiencies. The need was identified to leverage and meld together selected aspects of these various technologies. More specifically, there is a need to accommodate large numbers of increasingly mobile users, while at the same time providing enhanced levels of data communication service.
One particular need is a way to communicate data to and from a mobile computing device. Data communication must be fast and reliable, notwithstanding that the computer or other mobile device may be moving all over the planet in unpredictable ways. Mobile data communications must also be compatible with existing networks and protocols--a major paradigm shift is not commercially viable.